Temperature control method for use in a fusing device of an image forming apparatus having a fusing roller and a heater heating the fusing roller and image forming apparatus using the same

Abstract

A temperature control method for use in a fusing device of image forming apparatus having a fusing roller and a heater heating the fusing roller, including: sensing a surface temperature T of the fusing roller at one of when the image forming apparatus is turned on, when the image forming apparatus begins a normal operation from a power saving operation, and when a cover of the image forming apparatus is closed after being opened; comparing the sensed surface temperature T of the fusing roller with a set temperature; driving the heater until the surface temperature T reaches a first target temperature Tt 1 when the sensed surface temperature T is below the set temperature; and driving the heater until the surface temperature T reaches a second target temperature Tt 2 when the sensed surface temperature T is over the set temperature.

1. A temperature control method for use in a fusing device of image forming apparatus having a fusing roller and a heater heating the fusing roller, comprising:
 sensing a surface temperature T of the fusing roller at one of when the image forming apparatus is turned on, when the image forming apparatus begins a normal operation from a power saving operation, and when a cover of the image forming apparatus is closed after being opened;  
 comparing the sensed surface temperature T of the fusing roller with a set temperature;  
 driving the heater until the surface temperature T reaches a first target temperature Tt 1  when the sensed surface temperature T is below the set temperature; and  
 driving the heater until the surface temperature T reaches a second target temperature Tt 2  when the sensed surface temperature T is over the set temperature,  
 wherein the first target temperature Tt1 is one of a temperature Tv so that the surface temperature T of the fusing roller is increasable to the third target temperature Tt3 when the heater is turned off after heating the surface temperature T of the fusing roller to the first target temperature Tt1, and a temperature higher than the temperature Tv.  
 
   
   
     2. The method of  claim 1 , wherein the driving the heater until the surface temperature T reaches the second target temperature Tt 2  includes driving the heater for a first on-time calculated by the following formula every first control period T 1 , wherein:
   first on-time (ms)=T 1 ×(α 1 ×( T−Tt   2 )+β 1 )/100,  
 
     and wherein α 1  is a first proportional factor and β 1  is a first offset value set according to the second target temperature Tt 2 . 
   
   
     3. The method of  claim 2 , wherein the first proportional factor α 1  is determined by the second target temperature Tt 2  and a rising slope in the surface temperature T of the fusing roller. 
   
   
     4. The method of  claim 2 , wherein the first offset value β 1  is settable by a first value, by which the surface temperature T of the fusing roller is maintainable at the second target temperature Tt 2  when the heater is driven only for an on-time calculated by the formula of T 1 ×β 1 /100 every first control period T 1  after the surface temperature of the fusing roller has reached the second target temperature Tt 2 , and a second value less than the first value. 
   
   
     5. The method of  claim 1 , further comprising standing by by controlling the driving of the heater to maintain the surface temperature T at a third target temperature Tt 3  after the sensing, comparing and driving operations. 
   
   
     6. The method of  claim 5 , wherein the standing by includes driving the heater for a second on-time calculated by the following formula every second control period T 2  to maintain the surface temperature T at the third target temperature Tt 3 , wherein:
   second on-time (ms)=T 2 ×(α 2 ×( T−Tt   3 )+β 2 )/100,  
 
     and wherein α 2  is a second given proportional factor and β 2  is a second offset value set according to the third target temperature Tt 3 . 
   
   
     7. The method of  claim 6 , wherein the second proportional factor α 2  is determined by the third target temperature Tt 3  and a rising slope in the surface temperature T of the fusing roller. 
   
   
     8. The method of  claim 6 , wherein the second offset value β 2  is one of a value V by which the surface temperature T of the fusing roller is maintained at the third target temperature Tt 3  when the heater is driven only for an on-time calculated by the following formula every second control period T 2 , and a value less than the value V, wherein:
   on-time= T   2 ×β 2 /100.  
 
   
   
     9. The method of  claim 1 , wherein the second target temperature Tt 2  is the same temperature as the third target temperature Tt 3 , the third target temperature Tt 3  being a print standby temperature. 
   
   
     10. The method of  claim 2 , wherein the first proportional factor α 1  is one of the same value as the second proportional factor α 2  and a value larger than the value of the second proportional factor α 2 . 
   
   
     11. The method of  claim 5 , further comprising printing by controlling the driving of the heater to maintain the surface temperature T at a fifth target temperature Tt 5  when a print command is input in the standing by. 
   
   
     12. The method of  claim 11 , wherein the printing comprises:
 driving the heater until the surface temperature T reaches a fourth target temperature Tt 4 ; and  
 controlling the driving of the heater to maintain the surface temperature T at the fifth target temperature Tt 5 .  
 
   
   
     13. The method of  claim 12 , wherein the operation of controlling the driving of the heater to maintain the surface temperature T at the fifth target temperature Tt 5  comprises:
 driving the heater when a surface temperature T of the fusing roller sensed every third control period T 3  is below the fifth target temperature Tt 5 ; and  
 stopping the driving of the heater when the surface temperature T of the fusing roller sensed every third control period T 3  is over the fifth target temperature Tt 5 .  
 
   
   
     14. The method of  claim 13 , wherein in the stopping the driving of the heater, when the surface temperature T of the fusing roller is greater than fifth target temperature Tt 5 , and the heater is driving and a heater driving time has not lapsed, the heater is continuously driven until the heater driving time lapses. 
   
   
     15. The method of  claim 14 , wherein the fourth target temperature Tt 4  is one of the same temperature as the fifth target temperature Tt 5  and a temperature higher than the fifth target temperature Tt 5 . 
   
   
     16. The method of  claim 5 , further comprising saving power by carrying out a power saving operation when a print command is not input even though a standby time T 4  has lapsed in the standing by. 
   
   
     17. The method of  claim 16 , wherein the power saving comprises:
 determining whether the print command is input every fifth control period T 5  after a lapse of the standby time T 4 ; and  
 controlling the driving of the heater to maintain the surface temperature T at a sixth target temperature Tt 6  when the print command is not input.  
 
   
   
     18. The method of  claim 17 , wherein the controlling the driving of the heater to maintain the surface temperature T at the sixth target temperature Tt 6  comprises driving the heater for a third on-time calculated by the following formula every fourth control period T 5 , wherein:
   third on-time (ms)= T   5 ×(α 3 ×( T−Tt   6 )+β 3 )/100,  
 
     and wherein α 3  is a third given proportional factor and β 3  is a third offset value set according to the sixth target temperature Tt 6 . 
   
   
     19. The method of  claim 18 , wherein the sixth target temperature Tt 6  is settable by an appropriate temperature below the third target temperature Tt 3  that is a print standby temperature. 
   
   
     20. The method of  claim 16 , wherein the power saving comprises:
 determining whether the print command is input after a lapse of the standby time T 4 ; and  
 stopping the driving of the heater when the print command is not input.  
 
   
   
     21. The method of  claim 1 , wherein the fusing roller comprises a rubber layer formed in a given thickness on a surface thereof. 
   
   
     22. The method of  claim 18 , wherein the third offset value β 3  is settable by one of a first value, by which the surface temperature T of the fusing roller is maintainable at the third target temperature Tt 3  when the heater is driven only for an on-time calculated by the formula of T 5 ×β 3 /100 every fourth control period T 5  after the surface temperature T of the fusing roller has reached the sixth target temperature Tt 6 , and a second value less than the first value. 
   
   
     23. The method of  claim 17 , wherein the power saving includes determining whether the print command is input after the lapse of the standby time T 4 , and stopping the driving of the heater when the print command is not input.